Disposal of sewage containing human or animal excrement through discharge into septic tanks, settling ponds or cess pools is complicated by the presence of sludge from fecal matter which slows or even blocks the disposal of liquid components by percolation and is objectionable in the use of the sewage for such agricultural purposes as irrigation. While some reduction of sludge occurs through the action of microorganisms present or added to tanks, ponds, or pools, the process is slower than is desired and generates noxious odors including hydrogen sulfide.